Without intending to limit the uses to which the present invention may be put, by way of example, applicant is aware of the present use of vent caps which are typically mounted on hinges onto the roofs of recreational vehicles such as camper trailers to selectively cover apertures formed in those roofs which serve as air vents providing circulation into the interior of the enclosure. Such prior art vent caps afford a relatively simple mechanism for the exchange of air from within the enclosure of the recreational vehicle so as to typically provide cooling. Quite often a mechanical hand crank is mounted into the frame supporting the vent cap so that a user may simply turn the hand crank to either open or close the vent cap over the air vent.
Such prior art air vents are, in applicant's experience, typically made of simply a single layer of for example plastic which provides very little insulation when, as is quite often the case, the outside temperature is sufficiently cool so that it is desirable to close the vent cap and heat the enclosure. For recreational vehicles, such a temperature differential will cause condensation on the inside of the vent cap, which may lead to roof rot, that is, by minimizing condensation, water will not penetrate the inside substructure of the recreational vehicle and promote roof decay. Further, heating the enclosure will often mean using up reservoirs of gaseous fuel carried on the exterior of the recreational vehicle such as in propane tanks. Consequently, in order to, minimize condensation and to preserve the fuel reserves, it is desirable to provide as much insulation in the vent cap as is economically feasible for the recreational vehicle. In the converse case quite often the outside temperature is greater than the inside temperature. For this situation a recreational vehicle is often equipped with air conditioning. In such instances, opening the vent cap will not cool the interior of the recreational vehicle because the outside temperature is hot, even at night, and so using air conditioning is often the only viable alternative to provide comfort within the enclosure of the recreational vehicle. Thus, again, it is advantageous to provide an insulated vent cap so as to minimize the heating of the air in the enclosure by heat transfer through the vent cap from the exterior of the recreational vehicle.